Categories set via Android can sometimes be prefixed by "System Group: ", for example "System Group: Friends" On Android, it is not possible to change this into "Friends" unfortunately.

The Thunderbird Preferences / SOGo / Contact Categories tab should offer an extra checkbox called:
Hide "System Group: " from contact categories in address book
which is enabled by default.

This should hide "System Group: " when categories are shown in Thunderbird address books. That is, when they are shown as information or when they are shown to choose from. In the Preferences / SOGo / Contact Categories tab, they should be shown as is.

Some additional help text could be added to inform the user that Android can have default categories with this prefix which cannot be changed by the user and that this option is offering a nices view to the same categories in order to keep them compatble.

Implementing this provides the user the shorter and frienlier names of categories they expect to see and expect to be able to choose from.